I'm almost ready to attempt adding YM2612 capabilities but I need to fix a fix discrepancy. If you toggle "Use Drop-In Core" the PSG sounds incorrectly detuned; the drop-in core is mine, and if I can get it working properly I can add other JS ports of VGM sound cores as needed.

WIP YM2612 support is added, but need help debugging; seems at best only the first three FM channels are output (which means there's a problem w/my port 2 code), and at worst it's outputting the wrong audio period). Given my experience the other day working on the PSG, I wouldn't be surprised if it was an issue getting C's typecasting abilities mimicked incorrectly in my code.